The present invention relates to a method for exfoliating a detached member, and in particular, a transferring method for exfoliating a transferred layer comprising a thin film such as a functional thin film and for transferring it onto a transfer member such as a transparent substrate. Also, the present invention relates to a transferring method of a thin film device, a thin film device, a thin film integrated circuit device, and a liquid crystal display device produced using the same.
Production of liquid crystal displays using thin film transistors (TFTs), for example, includes a step for forming thin film transistors on a transparent substrate by a CVD process or the like.
The thin film transistors are classified into those using amorphous silicon (a-Si) and those using polycrystalline silicon (p-Si), and those using polycrystalline silicon are classified into those formed by a high temperature process and those formed by a low temperature process.
Since the formation of such thin film transistors on a substrate involves treatment at a relatively high temperature, a heat resistant material, that is, a material having a high softening point and a high melting point must be used as the transparent substrate. At present, in the production of TFTs by high temperature processes, transparent substrates composed of quartz glass which are sufficiently resistive to a temperature of approximately 1,000° C. are used. When TFTs are produced by low temperature processes, the maximum process temperature is near 500° C., hence heat-resisting glass which is resistive to a temperature near 500° C. is used.
As described above, a substrate for use in forming thin film devices must satisfy the conditions for producing these thin film devices. The above-mentioned “substrate” is, however, not always preferable in view of only the steps after fabrication of the substrate provided with thin film devices is completed.
For example, in the production process with high temperature treatment, quartz glass or heat-resisting glass is used, however, they are rare and very expensive materials, and a large transparent substrate can barely be produced from the material.
Further, quartz glass and heat-resisting glass are fragile, easily broken, and heavy. These are severe disadvantages when a substrate provided with thin film devices such as TFTs is mounted into electronic units. There is a gap between restriction due to process conditions and preferred characteristics required for products, hence it is significantly difficult to satisfy both the restriction and characteristics.
The present invention has been achieved in view of such a problem, and has an object to provide an exfoliating method, which permits easy exfoliation regardless of characteristics of the detached member and conditions for exfoliating, and transferring to various transfer members. Another object is to provide a novel technology which is capable of independently selecting a substrate used in production of thin film devices and a substrate used when the product is used (a substrate having preferable properties for use of the product). A further object is to provide a novel technology not causing deterioration of characteristics of thin film devices which are transferred onto a substrate, by decreasing the optical energy radiated to the separable layer causing ablation in the transferring process.